the powers that be; those in power at the time
Refers to the people or group holding political or social authority at a particular time, often with a nuance of transience or criticism.
See also: 権力者
It is dangerous to defy the powers that be.
He got ahead by currying favor with those in power at the time.
権力者 simply means 'powerful person' or 'authority figure' in general, while 時の権力者 specifically emphasizes the temporal nature of that power, often implying it may not last.
A set phrase composed of 時 (time) + の (possessive particle) + 権力者 (person in power), literally 'the powerful person of the time'.